1. Field of the Invention
The subject invention relates to methods and apparatus for transferring information, such as information recording, writing, reproducing or reading methods and apparatus of an optical, magnetic or other type, and to components for such apparatus, including, for instance, rollers and recording medium guides, and to methods for making same.
2. Disclosure Statement
The disclosure statement is made pursuant to the duty of disclosure imposed by law and formulated in 37 CFR 1.56(a). No representation is hereby made that information thus disclosed in fact constitutes prior art, inasmuch as 37 CFR 1.56(a) relies on a materiality concept which depends on uncertain and inevitably subjective elements of substantial likelihood and reasonableness, and inasmuch as a growing attitude appears to require citation of material which might lead to a discovery of pertinent material though not necessarily being of itself pertinent. Also, the following comments contain conclusions and observations which have only been drawn or become apparent after conception of the subject invention or which contrast the subject invention or its merits against the background of developments subsequent in time or priority.
The expediency of bending a recording medium for recording and playback purposes has long ago been recognized as may, for instance, be seen from U.S. Pat. No. 1,735,335, by F. H. Owens, and U.S. Pat. No. 1,865,055, by T. W. Case, where photographic film is shown as bent over a drum or curved guide for information transducing purposes, and is held in its bent condition by curved finger or track elements. Such an approach in practice has been feasible for relatively low recording medium speeds and in processes where the information transducing function concerns only part of the width of the recording medium.
A better utilization of the recording medium was obtained with the use of mechanical scanners, such as those illustrated in U.S. Pat. No. 3,314,075, by C. H. Becker et al, showing a coherent light beam recorder in which a recording medium is advanced in an arc about a cylindrical space which contains rotating scanner equipment similar in principle to the rotating heads in a helical scan magnetic tape recorder. That approach, however, has serious design limitations in that the scanning feature is in effect restricted to radially acting equipment and in that the recording medium, though having to be accurately guided and supported during advancement through an arc, at the same time has to be kept free for exposure to the rotating scanner.
A similar approach, resembling transverse scanning in magnetic tape recording, is apparent from U.S. Pat. No. 3,463,882, by R. J. Herbold, and U.S. Pat. No. 3,874,621, by L. R. Blair et al, where an advancing recording medium is bent transversely to its longitudinal direction for transverse scanning purposes by rotating mirror optics.
In practice, that approach requires an arcuate supporting and medium shaping structure, such as a vacuum platen, that is bound to exert considerable friction on the advancing medium. Where a concave air platen is employed to reduce friction in the manner of an air bearing, an air jet system has to be utilized, which tends to introduce disturbing factors, such as blown contaminants and moisture or excessive desiccation of the recording medium.
A compromise solution is apparent from the book THE PRINCIPLES AND PRACTICE OF FACSIMILE COMMUNICATION by Daniel M. Costigan (Chilton Book Company, 1971), p. 54, FIG. 3.8, where a facsimile system is shown in which a record is concavely curved and advanced by a lead screw mechanism relative to a revolving lens turret which thus scans the advancing record continually from side to side. In practice, that approach is limited to records of relatively short length, requiring special manipulations for the placement and removal of each record or recording medium. Attempts at mechanizing such requisite operations lead to complex systems as may be seen from U.S. Pat. No. 3,654,624, by C. H. Becker et al, where a rotating drum and galvanometer-type scanner system have been proposed for the purpose of handling a plurality of recording material strips which have to be specially indexed and retrieved.
A system designed for flat recording media and records is, for instance, apparent from U.S. Pat. No. ',501,586, by J. T. Russell, which employs rotating optical scanners.
According to one disclosed approach, a rotating scanner mirror is also axially moved in an effort to provide compensation for the flatness of the record. This in practice leads to a relatively complex scanner structure. Another disclosed approach equips the flat record or recording medium with a concave field corrector plate in the form of a negative lens. This in practice tends to cause light and reflection losses.
A somewhat similar approach appears from U.S. Pat. No. 4,168,506, by S. L. Corsover, in which a flat field lens has been proposed for focusing a scanning beam from a rotating polyhedric mirror onto a transversely scanned film which is advanced along a pair of cylinder guides that are curved transversely to the scanning direction. As that proposal points out, a suitable field lens needs to be composed of a plurality of lens elements.
Where a flat recording medium is held stationary during scanning with a rotating scanner, such scanner structure could be displaced relative to the stationary recording medium. However, displacement of a rotating scanner in parallel to its axis of rotation poses considerable problems in terms of equipment and tracking accuracy.